1 / 53

B physics at the Tevatron

B physics at the Tevatron. Brad Abbott University of Oklahoma. SLAC April 19, 2005. B physics at Hadron Colliders. Disadvantages: Large backgrounds Triggering and reconstruction difficult g and p 0 modes challenging. Advantages: Large cross sections ~100 m b

leon
Download Presentation

B physics at the Tevatron

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. B physics at the Tevatron Brad Abbott University of Oklahoma SLAC April 19, 2005

  2. B physics at Hadron Colliders • Disadvantages: • Large backgrounds • Triggering and reconstruction • difficult • g and p0 modes challenging Advantages: Large cross sections ~100 mb Produce all B species: Bu, Bd Bs, Bc, Lb,, …. Incoherent production

  3. DØ Both Detectors Silicon vertex detectors Central tracking High rate DAQ Calorimetry Muon systems CDF Strengths CDF: Silicon vertex trigger Particle ID(dE/dx and TOF) Excellent mass resolution DØ: Excellent electron and muon ID Large acceptance

  4. Luminosity • Tevatron doing very well Peak Luminosity doubled in 2004 1 x 1032 cm-2 s-1 Expect twice data in 2005 • Both experiments have • ~ 600 pb-1 on tape CDF: 240-360 pb-1 for results DØ: 220-460 pb-1 for results

  5. Analyses: • Focus on measurements complimentary to those at B-factories • Bs, Bc, Lb, … (Modes not accessible at B-factories) • Can contribute in a few places accessible to B-factories: B+f K+, Bdm m, lifetimes… • Often use lifetimes, Bd mixing, etc. as calibration measurements.

  6. Analysis strategy • Need to work with modes that can be triggered on • J/y m m (trigger on dimuons) • Semileptonic decays: trigger on lepton • Hadronic decays (trigger on track impact parameter (CDF), trigger on lepton from “other” B. DØ strength CDF strength Note: Need to apply Pt cuts on leptons to reduce rate and impact parameter trigger biases lifetimes.

  7. Wide range of Analyses • Measuring various B decays • Bc,B hh, b sss • Lifetimes • B+/B0, Lb, Bs semileptonic • Excited states • B**, D**, BsDs(2536) m n • Rare decays • Bs/Bd  mm, Bs mmf • Bs mixing, DG/G • Quarkonia, B hadron masses, Production cross sections, bb correlations, hadronic moments, charm physics,…

  8. Bc • Bc challenging. Low production rate B+,B0:40%, Bs,B baryons: 10%, Bc~ .05% • Factor of 3 shorter lifetime so cannot apply long lifetime cuts to reduce backgrounds • First observed in 1998 by CDF in BcJ/y +lepton n • DØ observed Bc in this mode in 2004 • Want to measure properties of Bc

  9. BcJ/yp • New CDF blind analysis • “score” function S/(1.5+sqrt(B)) set in advance • Reference mode B+J/y K+ First evidence of Bc J/yp Mass of Bc = 6.2870 ± 0.0048(stat) ± 0.0011(sys) GeV/c2 ~ 100 times better than previous mass measurement

  10. 95 ± 12 ± 11 signal events BcJ/ym(e)n J/ym X • Easy trigger: J/ymm • Can only partially reconstruct due to n M(Bc)=5.95 +0.14 – 0.13 ± 0.34 GeV/c2 tBc= 0.448 +0.123 – 0.096 ± 0.121 ps Critical issue is understanding background bb, conversion e and fake e 114 ±15.5 ± 13.6 events J/y e X

  11. B  hh • Charmless two-body decays • Can measure BR and direct CP asymmetry • Signal is composed of 4 different decays • Bdp+p- • BdK+p- • BsK+K- • Bsp+K- Displaced track trigger, PID and mass resolution critical

  12. B  hh = -0.04 ± 0.08 (stat+sys)

  13. b sss BR(Bsff) = 1.4 ± 0.6 ±0.2 ± 0.5) x 10 -6 Acp(B± fK±)= -0.07 ± 0.17(stat) ± 0.03(sys) First observation of this mode 12 candidates on 1.95 expected background events

  14. DØ DØ Lb lifetime • Fully reconstructed LbJ/y L DØt= 1.22 +0.22 – 0.18 ± 0.04 ps CDF t=1.25 ± 0.26 ± 0.10 ps World average: t=1.232 ± 0.072 ps Good agreement with HQE

  15. Observation of B m n D** X • D** are orbitally excited D meson states • In heavy quark limit • Two narrow states (D-wave) • Two broad states(S-wave) • Search for narrow states via • D01(2420)  D*+p- • D*02(2460) D*+ p-

  16. DØ M(D1) = 2021.7 ± 0.7 ± 0.6 GeV G(D1)=20.0 ± 1.7 ± 1.3 M(D2) = 2463.3 ± 0.6 ± 0.8 GeV G(D2) = 49.2 ± 2.3 ± 1.3

  17. Branching ratio • Take experimentally measured number of D10 and D2*0 : N(D1)+N(D2*)=523  40 • Measure branching ratio of B m n D**(narrow) X, normalizing to known branching ratio (B D*+m n X) • Br(B {D10,D2*0} m n X • Br({D10,D2*0}  D*+p-) = 0.280  0.021(stat) ± 0.088(sys) % • Compare to LEP measurement of total D** Br (B D*+p m n X) = (0.48  0.10)% • ~ half the rate through narrow states

  18. DØ RunII Preliminary B** Similar to D** decays, we can have orbitally excited B’s 2 narrow and 2 wide states So far only narrow states have been found. B** provide a good test of heavy Quark symmetry Many properties of B** unknown Soon can begin to measure many properties of B**

  19. DØ Run II Preliminary Evidence for BsDs1(2536) m X 3 s significance. Future hope to be able to measure its properties

  20. Bd,sm+ m- • Forbidden at Tree Level in SM Theoretical predictions Experimental limits at 90% CL

  21. Bsm+ m- in SUSY(Two Higgs-Doublet Model) • BR depends only on charged Higgs mass and tan b • BR increases as tan4b(tan6b) in 2HDM (MSSM) • R parity violating models can give tree level contributions

  22. Blind analyses • Isolation of the muon pair • Opening angle between momentum vector of mm pair and vector pointing from primary vertex to mm vertex • Decay length • Optimize using signal MC and data sidebands

  23. DØ Run II Preliminary Rare decays 240 pb-1 95% CL DØ: (Bs mm) < 3.7 X 10-7 CDF(Bs mm) < 2.0 X 10-7 CDF(Bd mm) < 4.9 x 10-8 World’s best limits CDF new multivariate analysis No strong MSSM limits from Bs. Too many MSSM parameters

  24. Bsm m f DØ Signal box not yet opened Expected sensitivity = 1.2 x 10-5

  25. Dipion mass Spectrum of the X(3872) • Nature of the X(3872) is still unknown. • Seen by Belle, CDF, DØ and BaBar • Still do not know its nature • cc or DD molecule or ?... • Found only in X J/yp+ p- • Various interpretations lead to different M(pp) distributions,

  26. X(3872) dipion mass distribution Rule out some interpretations

  27. DG/G using Bs J/yf • Main measurement is lifetime difference in Bs system We assume no CP violation in theBssystem and measuretwoBslifetimes,tLandtH, (orDG/Gandt) by simultaneously fitting the time evolution and angular distribution ofuntagged Bs J/y fdecays • Exploring CP violation beyond SM Weallow for a free CP violating angledf, and use the relation between themeasured DG/G, and SM prediction, DG/GSM, DG/G = DG/GSM cos2(df)to extractdf I. Dunietz, R. Fleischer, and U. Nierste, hep-ph/0012219

  28. Untagged Bs Rate in Time, Decay Angles CDF  =transversity

  29. 3 Angles  1 Angle Inserting H( cos) =1, and F() =1 + J cos(2) + K cos2(2), and integrating over cos and , we obtain a 1-angle time evolution: DØ = 0.355 ± 0.066 (from CDF)

  30. CDF th= 2.07 +.58 -.46 ± .03ps tL=1.05 + .16 - .13 ± .02 ps DG/G = 0.65 +.25 - .33 ± 0.01 DG=.47 + .19 - .24 ± .01 ps-1

  31. DØ Results  (in ps) R  /  tL (in ps)tH (in ps) (CP odd fraction at t=0)

  32. Add in World Average based on semileptonic decays Flavor specific final states (e.g. B0slDs ) provide:

  33. New Physics? We measure DG/G = DG/GSM cos2(df), where DG/GSM = 0.12 ± 0.05 (Lenz) SM predicts cos(df) ~ 1 Fit for cos2(df) gives: Consistent with SM

  34. Bs mixing • Important to measure Dms • Ratio of Dmd to Dms measures Vtd/Vts so we can apply tight constraints to Unitarity triangle • Current limits Dms > 14.4 ps-1 at 95% CL • Expect Dms < 24 ps-1 • New physics at 3 s if Dms > 30 ps-1 at 95% CL

  35. Measurement challenging • Large mixing frequency • Tagging quality • Messy environment Bd mixing Bs mixing Dms=20

  36. Semileptonic Large yields Poorer proper time resolution If Dms small, will find in semileptonic first Hadronic Smaller yields Better proper time resolution If Dms large, will need to use hadronic modes Semileptonic vs hadronic modes

  37. Hadronic samples • CDF: large samples but need to flavor tag • (eD2 ~ 1.12-1.43%) • DØ small samples but each event has a high Pt muon to provide tag (eD2 ~ 25%)

  38. Hadronic yields CDF yields 115±18 254±21 526± 33 S/B 1.0 1.7 1.8

  39. DØ hadronic modes L=250 pb-1 BdD*p L=70 pb-1 Not many events but each event has a high Pt muon for flavor tagging

  40. Semileptonic modes DØ Run II Preliminary Very Large sample m Ds sample Ds fp 460 pb-1 376 ± 31 events ~ 13K events

  41. ~ 7.6 K

  42. Biases due to trigger? ct = 413.8 ± 20.1 455.9 ± 11.9 422.6 ±25.7 Can correct for any trigger biases

  43. Fit and Results DØ Run II Preliminary BsDs+m- 400 pb-1 Green: signal Dotted line: background Dominant systematic: Background estimate, should be reduced in future World Average: 1.461 ± 0.057 ps t=1.420 ± 0.043 (stat) ± 0.057 (syst) ps

  44. DØ Run II Preliminary Flavor Tagging Muon Tag mD* Mistag rate: 27.6 ± 2.1% DMd consistent with world average Typical eD2 ~1-1.5%

  45. Measurement currently has no stand alone sensitivity

  46. DØ Run II Preliminary

  47. Future improvements CDF Statistics and propertime resolution!!!

  48. Future improvements to semileptonic Dms measurement DØ Short term

More Related